Paper products that are used for toweling and some types of tissues have several preferred but sometimes conflicting characteristics. For example, the products should have good bulk, a soft feel, and high absorbency of both water and oily liquids; yet the products should also have good tensile strength even while wet and resistance to "linting" of fibers from the toweling when rubbed. Processes that have aimed at achieving these objectives usually have utilized an initial substrate web of fibers which is formed with low internal bonding, such as is obtained from air laying or through-air-drying paper making processes, and have applied a wet strength binder to one or both sides of the web to provide the necessary tensile strength and resistance to linting. The liquid binder is customarily applied by passing the web through a nip between a gravure roller, which picks up the liquid binder, and a back-up or impression roller. Because of the pressure placed on the web at this nip and the migration of the binding liquid through the fibers of the web, the application of adhesive in this manner tends to result in an overall compaction and strengthening of the web.
One approach to reducing the strengthening effect is the use of a patterned gravure roller, as shown, e.g., in Roberts, Jr. U.S. Pat. No. 4,000,237, in which binding liquid is applied to the web over only a portion of the web surface. In this type of process, the web with binding liquid thereon is applied to a creping cylinder--with the binder acting as a creping adhesive--and is creped off to yield a product having a creping pattern which generally matches the pattern of binding liquid application. An overall compaction of the web still takes place at the nip between the gravure and back-up rollers and at the nip formed between the pressure roller and the surface of the creping cylinder.
Creping patterns may also be formed in the web by utilizing a patterned roller which presses an adhesive coated web against the creping cylinder, as shown in Klowak, et al., U.S. Pat. No. 4,125,659. The application of creping liquid to the web is uniform, and any additional strenthening of the web results only from the compaction of the web under the patterned roller.
Greater bulk and absorbency may be obtained in a laminate web of two or more plies than in a single layer web of equivalent size and weight. Multiple ply products can have greater absorbency than equivalent weights of single ply products because the small voids left between the plies are capable of absorbing and holding substantial quantities of liquid by capillary action. Bonding of multiple plies is usually carried out in straightforward fashion by applying a binding liquid to one or more of the plies and then pressing the plies together in a nip between two calendar rolls. The resulting product is again compressed over its entire area which thus tends to reduce its potential bulk, absorbency, and softness.